Project Summary Sheet

Study Title: Paleosalinity as a Key for Success Criteria in South Florida Restoration
Study Start Date: 10/01/2000 Study End Date: 9/30/05
Web Sites: http://sofia.usgs.gov/flaecohist/
Location (Subregions, Counties, Park or Refuge): Everglades National Park, Monroe County
Funding Source: USGS-PES
Principal Investigator(s): G. Lynn Wingard
Study Personnel: Thomas Cronin; Chuck Holmes; James Murray; and Robert Stamm (US Geological Survey); Gary Dwyer (Duke University)
Supporting Organizations: South Florida Water Management District; Everglades National Park

Associated / Linked Studies: Historical Changes in Salinity, Water Quality and Vegetation in Biscayne Bay; Ecosystem History of the Southwest Coast-Shark River Slough Outflow Area; Monitoring Sub-Aquatic Vegetation through Remote Sensing: A pilot study in Florida Bay.

Overview & Objective(s): There are three primary objectives to this project: 1) Develop a high resolution methodology to analyze the variability in shell chemistry of select marine/estuarine organisms as a proxy to changes in water quality and source, 2) Develop an understanding of the biology of the selected organisms such that the variations in shell chemistry may more accurately reflect the temporal and spatial variability of both water quality and source, 3) Apply this technique to shells found in sediment cores that span the last 100-300 years of South Florida history in order to determine the seasonal variation in salinity and water sources prior to significant human alteration of the environment. These data will provide resource managers with the necessary information to establish targets and performance measures as restoration of more natural timing and delivery of water proceeds.

Status: Progress has been made in four general areas. 1) Calibration of ostracode Mg/Ca ratios to instrumental salinity (Robblee, unpublished data) readings has shown that ostracode Mg/Ca can accurately predict salinity to within 1-4 ppt. Additional modern work on calibration of ostracode shells to water chemistry has been completed in association with the Biscayne Bay study and a report prepared. 2) Experimental work on molluscan shell chemistry and growth is continuing. Successful growth of Chione shells under known water conditions has been achieved both in the lab and the field; these shells and their associated water chemistry are currently being analyzed. Additional molluscan experiments are being conducted that a) use Sr as a marker to tag the shell for growth and water chemistry measurements, b) test growth, and c) test tolerances of common south Florida mollusks to salinity, temperature, and nutrient loads. These experiments supplement our field observations to provide a more complete proxy data set for all ecosystem history studies. 3) High resolution, semi-quantitative electron microprobe analyses have been completed on ten Chione specimens. Eight of these specimens are from Florida Bay field habitats, and two from controlled laboratory aquaria systems. 4) A statistical method of deriving a single salinity value from molluscan percent abundance assemblage data has been developed and compared to instrumental readings. With additional experimental data on molluscan salinity tolerances (developed under item 2) this statistical method will enhance accuracy of salinity estimates from cores.

Recent Products: A summary chapter on the Ecosystem History of Florida Bay, with the emphasis on Paleosalinity was generated for the Florida Bay PMC synthesis and has been reviewed for publication in an FMRI bulletin.

Planned Products: Open file reports on a) the molluscan salinity and temperature tolerance experiments and b) the shell chemistry analyses will be completed in Fall 04, along with companion fact sheets summarizing the work. Also, an OFR summarizing significant field observational data on mollusks will be completed in FY05. Once experimental work is completed a journal article will be compiled.

Specific Relevance to Information Needs Identified in DOI's Science Plan in Support of Ecosystem Restoration, Preservation, and Protection in South Florida (DOI's Everglades Science Plan) [See Plan on SOFIA's Web site: http://sofia.usgs.gov/publications/reports/doi-science-plan/]:

One of the primary DOI activities discussed in the DOI Science Plan is to “ensure that hydrologic performance targets accurately reflect the natural predrainage hydrology and ecology” (DOI Science Plan, p. 14). The goal of the Paleosalinity study is to develop a high resolution method for interpreting short term (less than a decade) changes in salinity from calcareous organisms preserved in cores dating back 100-500 years. The results of this work are applicable to all USGS ecosystem history studies. Specifically this study supports the Florida Bay and Florida Keys Feasibility Study Project and the Additional Water for Everglades National Park and Biscayne Bay Feasibility Study Project, and it provides information relevant to the Combined Structural and Operational Plan (CSOP) and Landscape Modeling projects. This study supports these projects by 1) developing a tool that can be used to understand the predrainage hydrology, including the amount, timing and seasonality of freshwater delivered historically; and 2) providing modelers with data on historic conditions in order to set targets and performance measures that reflect natural hydrologic patterns.

This study supports the Florida Bay and Florida Keys Feasibility Study Project by addressing the questions 1) What are the links between impediment to circulation created by the causeway and the ecology of Florida Bay . . .?” (DOI Science Plan, p. 64), “What are the links between freshwater inflows to Florida Bay and the ecology of the bay?” (p. 65), and “What is the ecological response to hydrologic change?” (p. 66). .

This study supports the Additional Water for Everglades National Park and Biscayne Bay Feasibility Study by addressing the questions “What were the physical and ecological conditions in . . . Taylor Slough . . . prior to drainage and modification . . .” (DOI Plan p. 63), “What are the hydrologic targets needed to mimic historic flows . . . ? (p. 63).

Key Findings:

1. Synthesis of data from all paleoecology research done in Florida Bay to date has demonstrated that rainfall is the predominant driver of salinity variation in the Bay.
2. Comparison of Mg/Ca trace element record from sediment core ostracodes to instrumental salinity record from Florida Bay over the last 50 years has demonstrated that Mg/Ca accurately reflects salinity to within 1-4 ppt.
3. Semi-quantitative analyses of Chione shells from both field and laboratory growth studies reveal significant temporal variations in the distribution and concentration of Mg/Ca and Sr/Ca.